1. Field of the Invention
This invention relates to a process gas supply mechanism for use in atomic layer chemical vapor deposition (ALCVD) systems. More particularly, this invention relates to a process gas supply mechanism for ALCVD systems that can switch between the supply and nonsupply of a process gas or can effect high speed switching between or among the feed of a plural number of process gases.
2. Description of the Prior Art
The treatment operating modes used by CVD systems can be broadly classified into batch modes and continuous inflow modes. There is no requirement for flow rate control means for either the reactant gas or carrier gas when a CVD system is operated in a batch mode. In the batch mode, process gas is first supplied to the treatment compartment until the pressure reaches a specified value and the process gas supply line is then closed. The treatment compartment is subsequently exhausted by opening the exhaust line (see Morishita et al., Applied Surface Science, 112 (1997), pp. 198-204).
When a CVD system is operated in a continuous inflow mode, the gas flow rate can be controlled by using a capillary in each of the process gas supply lines (Pathangey et al., Vacuum Technology and Coating, May, 2000, pp. 33-41). The gas supplied to the treatment compartment is switched by the opening and closing of a valve for each gas. A mass flow controller can be used for control instead of a capillary, but a capillary offers the advantage of instantaneous stabilization of the gas flow.
In another mechanism known for supplying process gas to a device such as a CVD or epitaxial treatment compartment, the flow rate is stabilized by a line that branches the gas prior to supply of the gas. This mechanism uses a branch T-structure equipped with a pair of valves in order to direct the process gas to the treatment compartment or to the treatment compartment bypass. The two valves comprise the combination of a NO valve (valve normally open) and an NC valve (valve normally closed) and are simultaneously switched by the same signal.
A similar technology is disclosed in EP 0 664 449 B1 (Ronge et al.). Here, all or part of gas containing trace level impurity is mixed or branched into a diluent gas. In order to control the degree of dilution by adjusting the branched flow rate, a mass flow controller is disposed in the branch line, that is, in offline position. A zero gas condition is realized by branching all of the impurity-containing auxiliary flow. In this technology, the total flow rate of impurity-containing gas is restricted by orifices and the branched flow rate is controlled by a mass flow controller.
Problems to be Solved by the Invention
ALCVD processing is known as one form of CVD processing. In a typical ALCVD process, a first reactant gas and a second reactant gas are alternately fed into a treatment compartment with rapid alternation thereinbetween. This results in repetitive gas adsorption and reaction on the treatment substrate with the formation of a desired film through atomic layer-by-atomic layer deposition (atomic layer deposition). At the present time standard gas manifolds are used in CVD systems that carry out ALCVD processing.
The following problems are identified when one considers batch mode execution of ALCVD processing. First, evacuation and cyclic purging of the treatment compartment are required after supply of a first reactant gas into the treatment compartment and prior to supply of a second reactant gas. This yields a process that requires fairly long periods of time given the number of switching operations (from 20 to 1,000) required for ALCVD. Second, the number of operations by the inline valve (valve in the gas supply line to the treatment compartment) is also increased. Since particles are produced by the operation of a valve, the probability of contamination of the treatment substrate increases in direction proportion to the number of valve operations. The probability of contamination of the treatment substrate is therefore substantially raised when one considers the batch mode execution of ALCVD processing.
The following problems are identified when one considers execution of ALCVD processing by the continuous inflow mode. First, the number of inline valve operations is again an important factor in this mode. Second, taking as an example a structure as in the apparatus of Pathangey et al., supra, the gas may undergo nonuniform flow until the pressure stabilizes. Specifically, the gas may flow at a high flow rate immediately upon opening of the valve in the reactant gas line, and the flow rate may thereafter undergo a gradual stabilization. Third, when the valve closes, the reactant gas flow declines as the capillary empties, and the time required for this represents a period of equipment underutilization. Moreover, since lengthy time intervals are required for process stabilization at each step, the overall sequence requires substantial amounts of time.
This invention was developed in view of the problems delineated above for the prior art. The object of this invention is to provide a process gas supply mechanism for ALCVD systems which enables switching between process gas supply and nonsupply, or which can carry out high speed switching of the supply of a plural number of process gases, and which can in any case effect said switching without accompanying particulate contamination of the treatment substrate.
Means Solving the Problems
The first aspect of this invention is a process gas supply mechanism for ALCVD systems, wherein the ALCVD system is provided with a gastight treatment compartment that holds the treatment substrate and with a vacuum exhaust section that can exhaust said treatment compartment and is connected to the treatment compartment through an exhaust line, and wherein the process gas supply mechanism is connected to the treatment compartment in order to feed process gas into the treatment compartment, said process gas supply mechanism being characteristically provided with
a first reactant gas line that can supply a flow rate-regulated first reactant gas;
a first auxiliary gas line that can supply a flow rate-regulated first auxiliary gas;
a first vent line, which is connected to the first reactant gas line upstream from a first position at which the first reactant gas flow is combined with the first auxiliary gas flow;
a first vent setting means that is disposed in the first vent line and that can set the flow rate vf1 of the gas flowing in the first vent line so as to satisfy the condition mf1 less than vf1 less than sf1+mf1 wherein mf1 is the flow rate of the first reactant gas supplied from the first reactant gas line and sf1 is the flow rate of the first auxiliary gas supplied from the first auxiliary gas line;
a first vent switching means that is disposed in the first vent line and that can open and close the first vent line; and
a first drive control means that drives the first vent switching means in such a manner that the first vent switching means carries out its switching operation repetitively.
The second aspect of this invention has as its characteristic feature the additional provision in the mechanism of the first aspect of a first joint flow line that can supply gas to the treatment compartment and that is formed by the combination at the aforesaid first position of the first reactant gas line and the first auxiliary gas line.
The third aspect of this invention characteristically comprises the mechanism of the first or second aspect with the additional disposition therein of a second reactant gas line that can supply a flow rate-regulated second reactant gas; a second auxiliary gas line that can supply a flow rate-regulated second auxiliary gas; a second joint flow line, which supplies gas to the treatment compartment and is formed by the combination at a second position of the second reactant gas line and the second auxiliary gas line; a second vent line, which is connected to the second reactant gas line upstream from said second position; a second vent setting means that is disposed in the second vent line and that can set the flow rate vf2 of the gas flowing in the second vent line so as to satisfy the condition mf2 less than vf2 less than sf2+mf2 wherein mf2 is the flow rate of the second reactant gas supplied from the second reactant gas line and sf2 is the flow rate of the second auxiliary gas supplied from the second auxiliary gas line; a second switching means that is disposed in the second vent line and that can open and close the second vent line; and a second drive control means that drives the second switching means in such a manner that the second switching means repetitively effects its switching operation in a regime synchronized with the switching operation of the first switching means that provides a switched state opposite from that of the first switching means.
The fourth aspect of this invention is a process gas supply mechanism for ALCVD systems, wherein the ALCVD system is provided with a gastight treatment compartment that holds the treatment substrate and with a vacuum exhaust section that exhausts said treatment compartment and is connected to the treatment compartment through an exhaust line, and wherein the process gas supply mechanism is connected to the treatment compartment in order to feed process gas into the treatment compartment, said process gas supply mechanism being characteristically provided with a first reactant gas line that can supply a flow rate-regulated first reactant gas; a first auxiliary gas line that can supply a flow rate-regulated first auxiliary gas; a first joint flow line that supplies gas to the treatment compartment and is formed by the combination at a first position of the first reactant gas line and the first auxiliary gas line; a first reactant gas vent line, which is connected to the first reactant gas line upstream from the first position; a first auxiliary gas vent line, which is connected to the first auxiliary gas line upstream from the first position; a first reactant gas vent setting means that is disposed in the first reactant gas vent line and that can set the flow rate vf1m of the gas flowing in the first reactant gas vent line so as to satisfy the condition mf1 less than vf1m less than mf1+sf1 wherein mf1 is the flow rate of the first reactant gas supplied from the first reactant gas line and sf1 is the flow rate of the first auxiliary gas supplied from the first auxiliary gas line; a first auxiliary gas vent setting means that is disposed in the first auxiliary gas vent line and that can set the flow rate vf1s of the gas flowing in the first auxiliary gas vent line so as to satisfy the condition sf1 less than vf1s less than sf1+mf1; a first reactant gas vent switching means that is disposed in the first reactant gas vent line and that can open and close the first reactant gas vent line; a first auxiliary gas vent switching means that is disposed in the first auxiliary gas vent line and that can open and close the first auxiliary gas vent line; and a first drive control means that drives the first reactant gas vent switching means and the first auxiliary gas vent switching means, in such a manner that the first reactant gas vent switching means and the first auxiliary gas vent switching means carry out their switching operations repetitively in a regime synchronized to each other that provides opposite switched states for the two means.
The fifth aspect of this invention characteristically comprises the mechanism of the fourth aspect with the additional disposition therein of a second reactant gas line that can supply a flow rate-regulated second reactant gas; a second auxiliary gas line that can supply a flow rate-regulated second auxiliary gas; a second joint flow line, which supplies gas to the treatment compartment and is formed by the combination at a second position of the second reactant gas line and the second auxiliary gas line; a second reactant gas vent line, which is connected to the second reactant gas line upstream from said second position; a second auxiliary gas vent line, which is connected to the second auxiliary gas line upstream from said second position; a second reactant gas vent setting means that is disposed in the second reactant gas vent line and that can set the flow rate vf2m of the gas flowing in the second reactant gas vent line so as to satisfy the condition mf2 less than vf2m less than mf2+vf2 wherein mf2 is the flow rate of the second reactant gas supplied from the second reactant gas line and vf2 is the flow rate of the second auxiliary gas supplied from the second auxiliary gas line; a second auxiliary gas vent setting means that is disposed in the second auxiliary gas vent line and that can set the flow rate vf2s of the gas flowing in the second auxiliary gas vent line so as to satisfy the condition vf2 less than vf2s less than vf2+mf2; a second reactant gas vent switching means that is disposed in the second reactant gas vent line and that can open and close the second reactant gas vent line; a second auxiliary gas vent switching means that is disposed in the second auxiliary gas vent line and that can open and close the second auxiliary gas vent line; and a second drive control means that can drive the second reactant gas vent switching means and the second auxiliary gas vent switching means, in such a manner that the second reactant gas vent switching means and the second auxiliary gas vent switching means carry out their switching operations repetitively in a regime synchronized to each other that provides opposite switched states for the two means and synchronized to the switching operations of the first reactant gas vent switching means and the first auxiliary gas vent switching means and providing opposite switched states therefrom.
The sixth aspect of this invention characteristically comprises the mechanism of the fifth aspect with the additional disposition therein of a supply line which is formed by the combination at a third position of the first and second joint flow lines and which supplies gas to the treatment compartment; a first supply vent line, which is connected to the first joint flow line upstream from the third position; a second supply vent line, which is connected to the second joint flow line upstream from the third position; a first supply vent setting means, which is disposed in the first supply vent line and can set the flow rate f3a of the gas flowing in the first supply vent line so as to satisfy the condition f1 less than f3a less than f1+f2 wherein f1 is the flow rate of the gas supplied from the first joint flow line and f2 is the flow rate of the gas supplied from the second joint flow line; a second supply vent setting means, which is disposed in the second supply vent line and can set the flow rate f3b of the gas flowing in the second supply vent line so as to satisfy the condition f2 less than f3b less than f2+f1; a first supply vent switching means that is disposed in the first supply vent line and that can open and close the first supply vent line; a second supply vent switching means that is disposed in the second supply vent line and that can open and close the second supply vent line; and a third drive control means that can drive the first supply vent switching means and the second supply vent switching means through repetitive switching operations according to a regime in which the first supply vent switching means and the second supply vent switching means are synchronized and in opposite.
The seventh aspect of this invention characteristically comprises the mechanism of the sixth aspect in which the first and second supply vent lines are combined to form a common vent line and the first and second supply vent setting means comprise a common setting means that is disposed in the common vent line.
The eighth aspect of this invention characteristically comprises a mechanism according to any of the fourth to seventh aspects in which the reactant gas vent line and the auxiliary gas vent line are combined to form a joint flow vent line and the reactant gas vent setting means and auxiliary gas vent setting means comprise a common setting means that is disposed in said joint flow vent line.
The ninth aspect of this invention characteristically comprises a mechanism according to any of the third and fifth through seventh aspects, in which the first and second joint flow lines are themselves combined and thereafter connected to the treatment compartment through a supply line, and in which the process gas supply mechanism is additionally provided with a common pressure setting means that is disposed in the aforesaid supply line and can set the pressure in the first and second joint flow lines.
The tenth aspect of this invention characteristically comprises a mechanism according to any of the third, fifth through seventh, and ninth aspects, in which the first and second auxiliary gas lines branch from a common main line and a flow rate control means is disposed in said main line.
The eleventh aspect of this invention characteristically comprises a mechanism according to any of the third, fifth through seventh, ninth, and tenth aspects in which the first and second drive control means are provided with a common drive control element.
The twelfth aspect of this invention characteristically comprises a mechanism according to any of the first through eleventh aspects in which a pressure setting means is additionally disposed in the joint flow line in order to set the pressure in said joint flow line.
The thirteenth aspect of this invention characteristically comprises the mechanism according to the twelfth aspect in which the pressure setting means comprises an automatic pressure regulator that maintains the pressure within the joint flow line at a set pressure.
The fourteenth aspect of this invention characteristically comprises a mechanism according to any of the first through thirteenth aspects in which the vent switching means and vent setting means disposed in the same vent line comprise separate members and said vent switching means is disposed upstream from said vent setting means.
The fifteenth aspect of this invention characteristically comprises a mechanism according to any of the first through fourteenth aspects in which the vent setting means comprises a device that can alter the flow rate of the gas flowing in the vent line.
The sixteenth aspect of this invention characteristically comprises a mechanism according to any of the first through fifteenth aspects in which the vent line is connected to the exhaust line.